run-help is by default an alias to man, and can be redefined to a function (in Functions/Misc) that will look in other places before invoking man. It is bound to the key sequence: ALT-h (aka ESC-h).
The function can be further customized by defining helper functions of the form run-help-command. There are three such functions available in the standard distribution: run-help-git, run-help-svk, and run-help-svn.
To make use of the more advanced function (and three helpers), insert the following into your .zshrc
autoload -U run-help autoload run-help-git autoload run-help-svn autoload run-help-svk export HELPDIR=~/zsh_help